The present invention relates to a vibrating device mounted in a portable device such as a portable telephone and PDA (personal digital assistant), for transmitting information to a wearer.
FIG. 2 is a sectional view showing a conventional vibrating device disclosed in Japanese Patent Laid Open 7-107699.
The vibrating device 53 comprises a first assembly 51 and a second assembly 52 The first assembly 51 comprises a first frame 61 made of resin and having a dish-like shape and a vibrating assembly 66 resiliently supported in the first frame by an annular spring plate 62. The vibrating assembly 66 comprises a yoke 63 made of magnetic material comprising a center pole 63a and a flange 63b, an annular permanent magnet 64 secured to the flange 63b, and an annular top plate 65 made of magnetic material and secured to the permanent magnet 64. The underside of the first frame 61 is covered by a protector 67.
The second assembly 52 comprises a second frame 71 made of resin and secured to the first frame 61 at shoulders 61a and 71a, and an annular spring plate 72 embedded in the second frame 71 and secured to the top plate 65 for holding the vibrating assembly 66. A supporting plate 73 is secured to the second frame 71 to close the second frame 71. An annular driving coil 74 is secured to an annular projection 73a formed on the underside of the supporting plate 73. The coil 74 is inserted in a magnetic gap 66a between the center pole 63a and the top plate 65. The coil 74 is connected to a driving circuit through a terminal means 68.
When a signal current is applied to the driving coil 74, the vibrating assembly 66 vibrates. The vibration is transmitted to a wearer through the first frame 61 and a case of a portable device in which the vibrating device 53 is mounted.
The conventional vibrating device has disadvantages that the coil 74 breaks by lateral movement of the yoke 63a and top plate 65 when receiving external shock.
An object of the present invention is to provide a vibrating device a vibrating assembly of which is protected from external shock.
According to the present invention, there is provided a vibrating device comprising a frame, a vibrating assembly comprising a yoke having a center pole and a peripheral flange, an annular permanent magnet secured to the flange, and an annular top plate secured to the permanent magnet, supporting means for resiliently supporting the vibrating assembly in the frame, an annular driving coil inserted in a magnetic gap formed between the yoke and the top plate, preventing means for preventing the vibrating assembly from being moved in a radial direction of the vibrating assembly.
The device further comprises a cylindrical center piece secured in the center pole of the yoke.
The preventing means comprises a hole formed in the center piece at an axis, and a central shaft securely mounted in the frame and slidably engaged in the hole of the center piece.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.